This invention relates to a method and apparatus for drying a workpiece such as a substrate used in magnetic disk or integrated circuit manufacturing.
In many manufacturing processes it is necessary to treat a workpiece with a liquid and then dry the workpiece. For example, during the manufacturing of magnetic disks, one typically performs the following manufacturing steps:
1. First a nickel-phosphorus layer is plated onto an aluminum substrate; PA1 2. The nickel-phosphorus layer is polished and textured; PA1 3. The substrate is cleaned, rinsed and dried; PA1 4. A series of layers are sputtered onto the substrate, e.g., an underlayer such as sputtered NiP or Cr, a magnetic cobalt alloy, and a protective hydrogenated carbon overcoat.
Immediately prior to sputtering, the substrate is cleaned and then dried. It is extremely important that when the substrate is dried, there are no impurities left on its surface.
Numerous other manufacturing processes require drying a workpiece. For example, during various semiconductor manufacturing process steps, semiconductor wafers are immersed in a liquid and then dried. It is critical that there be no impurities on the surface of these wafers after drying.
One structure for drying semiconductor wafers is discussed in European Patent Application 0 385 536 A1, incorporated herein by reference. In the '536 apparatus, a cassette of wafers is immersed in a liquid and then slowly removed from the liquid in the presence of a vapor that aids in the drying process. The cooperation of this vapor and liquid creates the so-called Marangoni effect which permits drying of the wafer without leaving "drying marks".
During the drying process, a wafer holding mechanism is always in contact with the wafer. This leaves the possibility that there will be a contamination or drying mark at the point where the wafer is held during drying. One object of our invention is to overcome this problem.